fix: cargo test -p der now pass

der/src/asn1/context_specific.rs

@@ -22,7 +22,7 @@ pub fn decode_implicit<'a, R: Reader<'a>, T: Tagged + DecodeValue<'a>>(
     number: TagNumber,
     reader: &mut R,
 ) -> Result<Option<T>, T::Error> {
-    match AnyCustomClassImplicit::decode_implicit(Class::ContextSpecific, number, reader) {
+    match AnyCustomClassImplicit::decode_skipping(Class::ContextSpecific, number, reader) {
         Ok(Some(custom)) => Ok(Some(custom.value)),
         Ok(None) => Ok(None),
         Err(err) => Err(err),
@@ -33,7 +33,7 @@ pub fn decode_explicit<'a, R: Reader<'a>, T: Decode<'a>>(
     number: TagNumber,
     reader: &mut R,
 ) -> Result<Option<T>, T::Error> {
-    match AnyCustomClassExplicit::decode_explicit(Class::ContextSpecific, number, reader) {
+    match AnyCustomClassExplicit::decode_skipping(Class::ContextSpecific, number, reader) {
         Ok(Some(custom)) => Ok(Some(custom.value)),
         Ok(None) => Ok(None),
         Err(err) => Err(err),

der/src/asn1/custom_class.rs

@@ -44,7 +44,7 @@ impl<T, const TAG: u16, const CLASS: u8> CustomClass<T, TAG, CLASS> {
     where
         T: Decode<'a>,
     {
-        match AnyCustomClassExplicit::decode_explicit(Class::from(CLASS), TagNumber(TAG), reader) {
+        match AnyCustomClassExplicit::decode_skipping(Class::from(CLASS), TagNumber(TAG), reader) {
             Ok(Some(custom)) => Ok(Some(Self {
                 value: custom.value,
             })),
@@ -70,21 +70,21 @@ fn is_unskippable_tag(tag: Tag, expected_class: Class, expected_number: TagNumbe
 
 /// Attempt to decode a custom class-tagged field with the given
 /// helper callback.
-fn decode_with<'a, F, R: Reader<'a>, E, T>(
+fn decode_peeking<'a, F, R: Reader<'a>, E, T>(
     reader: &mut R,
     expected_class: Class,
     expected_number: TagNumber,
     f: F,
 ) -> Result<Option<T>, E>
 where
-    F: FnOnce(Tag, &mut R) -> Result<T, E>,
+    F: FnOnce(&mut R) -> Result<T, E>,
     E: From<Error>,
 {
     while let Some(tag) = Tag::peek_optional(reader)? {
         if is_unskippable_tag(tag, expected_class, expected_number) {
             break;
         } else if tag.number() == expected_number {
-            return Some(f(tag, reader)).transpose();
+            return Some(f(reader)).transpose();
         } else {
             AnyRef::decode(reader)?;
         }
@@ -104,7 +104,7 @@ impl<T, const TAG: u16, const CLASS: u8> CustomClassImplicit<T, TAG, CLASS> {
     where
         T: DecodeValue<'a> + Tagged,
     {
-        match AnyCustomClassImplicit::decode_implicit(Class::from(CLASS), TagNumber(TAG), reader) {
+        match AnyCustomClassImplicit::decode_skipping(Class::from(CLASS), TagNumber(TAG), reader) {
             Ok(Some(custom)) => Ok(Some(Self {
                 value: custom.value,
             })),
@@ -130,31 +130,46 @@ impl<'a, T> AnyCustomClassExplicit<T>
 where
     T: Decode<'a>,
 {
-    pub fn decode_explicit<R: Reader<'a>>(
+    pub fn decode_skipping<R: Reader<'a>>(
         class: Class,
         number: TagNumber,
         reader: &mut R,
     ) -> Result<Option<Self>, T::Error> {
-        decode_with(reader, class, number, |tag, reader| {
+        decode_peeking(reader, class, number, |reader| {
+            Self::decode(class, number, reader)
+        })
+    }
+
+    pub fn decode<R: Reader<'a>>(
+        class: Class,
+        number: TagNumber,
+        reader: &mut R,
+    ) -> Result<Self, T::Error> {
+        let header = Header::decode(reader)?;
+
+        if header.tag.class() == class {
             Ok(Self {
-                value: T::decode(reader)?,
-                tag_number: tag.number(),
-                constructed: tag.is_constructed(),
+                value: reader.read_nested(header.length, |reader| T::decode(reader))?,
+                tag_number: header.tag.number(),
+                constructed: header.tag.is_constructed(),
             })
-        })
+        } else {
+            let expected = expected_tag_constructed(class, number, true);
+            Err(header.tag.unexpected_error(Some(expected)).into())
+        }
     }
 }
 
 impl<'a, T> AnyCustomClassImplicit<T>
 where
     T: Tagged + DecodeValue<'a>,
 {
-    pub fn decode_implicit<R: Reader<'a>>(
+    pub fn decode_skipping<R: Reader<'a>>(
         class: Class,
         number: TagNumber,
         reader: &mut R,
     ) -> Result<Option<Self>, T::Error> {
-        decode_with::<_, _, T::Error, _>(reader, class, number, |_tag, reader| {
+        decode_peeking::<_, _, T::Error, _>(reader, class, number, |reader| {
             let header = Header::decode(reader)?;
             let value = T::decode_value(reader, header)?;
 
@@ -198,15 +213,11 @@ where
     type Error = T::Error;
 
     fn decode<R: Reader<'a>>(reader: &mut R) -> Result<Self, Self::Error> {
-        let header = Header::decode(reader)?;
-
-        if header.tag.class() == Class::from(CLASS) {
-            Ok(Self {
-                value: reader.read_nested(header.length, |reader| T::decode(reader))?,
-            })
-        } else {
-            let expected = expected_tag_constructed(Class::from(CLASS), TagNumber(TAG), true);
-            Err(header.tag.unexpected_error(Some(expected)).into())
+        match AnyCustomClassExplicit::<T>::decode(Class::from(CLASS), TagNumber(TAG), reader) {
+            Ok(custom) => Ok(Self {
+                value: custom.value,
+            }),
+            Err(err) => Err(err),
         }
     }
 }

der/src/reader.rs

@@ -56,13 +56,13 @@ pub trait Reader<'r>: Sized {
         T: DecodeValue<'r> + FixedTag + 'r,
     {
         Ok(match tag_mode {
-            TagMode::Explicit => AnyCustomClassExplicit::<T>::decode_explicit(
+            TagMode::Explicit => AnyCustomClassExplicit::<T>::decode_skipping(
                 Class::ContextSpecific,
                 tag_number,
                 self,
             )?
             .map(|field| field.value),
-            TagMode::Implicit => AnyCustomClassImplicit::<T>::decode_implicit(
+            TagMode::Implicit => AnyCustomClassImplicit::<T>::decode_skipping(
                 Class::ContextSpecific,
                 tag_number,
                 self,